The present invention relates to a display retaining and connecting device for portable apparatus and in particular a radiotelephone.
Two of the main objectives during the design of portable electrical equipment are that, first, the equipment should be easy to manufacture and, second, the equipment should be designed within a limited designated space envelope. One element that can be critical for achieving both these objectives is the connecting and retaining of a display to the equipment.
Examples of portable electrical equipment to which this applies are personal organisers, communicators, radiotelephones etc. During the assembly of the equipment the display is first electrically connected to a circuit board. The connection between the display, for example a LCD, and the circuit board, for example a PCB, is typically via a flexible tab type connector. Once the display is connected to the circuit board the display is then fixed within the equipment to prevent damage to the display and the electrical interface.
One commonly used technique for connecting a display to a radiotelephone circuit board is hot bar soldering.
The hot bar soldering technique requires that, first, solder is placed on the circuit board contacts which have been provided to supply current to the display. The display connector (e.g. the flexible tab connector) is placed on top of the circuit board contacts, sandwiching the solder between the flexible tab connector contacts and the circuit board contacts. A heating element (i.e. a hot bar) is then brought down on top of the flexible tab connector contacts. The heat from the hot bar is conducted through the flexible tab connector and contacts causing the solder to flow and electrically bond the flexible tab connector contacts with the circuit board contacts. Mechanical support is provided on the opposite side of the circuit board to prevent the hot bar damaging the circuit board when the hot bar is brought down on the flexible tab connector.
Another similar technique is heat bonding. The method of connecting the display connector to the circuit board is the same as for hot bar soldering. However, instead of using solder a conductive bonding material is used which is electrically conductive in only one axisxe2x80x94between the circuit board and the flexible tab connector.
These techniques, however, increase the complexity of the radiotelephone manufacturing process. The radiotelephone circuit board which, in use, provides current to the display typically has single sided placement of surface mounted components mounted on the opposite (i.e. second) side of the circuit board to the display. This allows the first side of the circuit board to be used for other purposes, for example placing touch sensitive switches for key selections and mounting the display. Therefore, during component placement the circuit board will move along the production line with the second surface facing upward to allow the surface mounted components to be connected to the circuit board. However, as the display has to be soldered to the opposite side of the circuit board to that of the components the circuit board has to be rotated onto its other side when connecting the display to the circuit board. Typically this requires that the hot bar soldering or heat bonding be performed off the production line at a separate station. This is time consuming and inefficient.
These techniques also increase the complexity of replacing a display. This may be necessary if, for example, the display is faulty.
It is also necessary for the display to be soldered to the circuit board at a separate station as typically the display can not withstand the temperatures of the re-flow ovens used for soldering the surface mounted components to the circuit board.
Further as these techniques require mechanical support on the underside of the circuit board, the side to which surface mounted devices are attached, this requires an area of unpopulated circuit board. This is wasteful of circuit board space, which can increase the overall size of the radiotelephone.
A third technique for connecting the display to the circuit board is the use of elastomeric connectors, commonly known as zebra strips. An elastomeric connector comprises an element of conductive columns. The elastomeric connector is placed between the display and circuit board contacts. The contacts are then clamped together. The connector is orientated between the display and circuit board contacts such that the conductive columns electrically bond the display and circuit board contacts. However, the contacts need to be mounted on stiff co-planer surfaces to allow the contacts to be clamped together. Further, as the number of contacts increases so increases the required clamping pressure. Therefore, for large numbers of contacts, which are typically encountered with LCD displays, elastomeric connectors can be unreliable.
Once the display has been connected to the circuit board the display is then secured to the radiotelephone to help prevent damage to the display and electrical interface. Typically, this is done by means of a metal retainer with a rubber gasket sandwiched between the LCD and metal retainer. The purpose of the rubber gasket it to absorb shock. This extra stage further increases complexity of the manufacturing process. The use of the gasket can also increase the size and cost of the radiotelephone.
In accordance with one aspect of the present invention there is provided a portable apparatus having a display retaining and connecting arrangement, the arrangement comprising a display having an electrical interface with at least one electrical contact; a circuit board having an electrical interface with at least one electrical contact for supplying current to the display; and a frame for securing the display to the portable apparatus and for urging the display contact and circuit board contact together to allow current to flow from the circuit board contact to the display contact.
This provides the advantage that the display can be attached and connected to the portable apparatus in one operation that can be performed on the production line. As extra mechanical support is not required on the circuit board during the manufacturing process extra space is available on the circuit board for components or conversely the circuit board can be made smaller.
Preferably the frame has a first section for securing the display to the portable apparatus and a second section for urging the display contacts and circuit board contacts together.
The second section will typically comprise a resilient element. Preferably the resilient element has a plurality of resilient fingers. A resilient finger is typically provided for each display contact thereby individually urging a display and circuit board contact together.
Preferably the first section is resiliently biased against the display to allow absorption of shock.
This avoids the requirement for an extra rubber gasket, which can result in a reduction in cost and size of the portable apparatus.
The frame can be pivotally mounted to the portable apparatus to allow movement between an open position and a closed position such that when the frame is in the open position the display can be positioned on or in the portable apparatus and when the frame is in the closed position the display can be secured to the portable apparatus and the display contact and circuit board contact can be urged together.
Further the portable apparatus or the frame can have retaining means for retaining the frame in the closed position.
Preferably the portable apparatus further comprises a speaker having an electrical contact, the frame being capable of securing the speaker to the portable apparatus and urging the speaker contact and a circuit board contact together to allow current to flow from the circuit board contact to the speaker contact.
Preferably the portable apparatus is a radiotelephone.
In accordance with a second aspect of the present invention there is provided a frame for mounting to a portable apparatus for retaining and electrically connecting a display to the portable apparatus, the frame comprising a first section for securing the display to the portable apparatus and a second section for urging together electrical contacts of the display and electrical contacts of portable apparatus together to allow current to flow from the portable apparatus contacts to the display contacts.
In accordance with a third aspect of the present invention there is provided a portable apparatus comprising a display having an electrical interface with at least one electrical contact; a circuit board having an electrical interface with at least one electrical contact for supplying current to the display; and a frame for urging the display contact and circuit board contact together to allow current to flow from the circuit board contact to the display contact.
In accordance with a fourth aspect of the present invention there is provided a portable apparatus comprising a display having an electrical interface with at least one electrical contact; a circuit board having an electrical interface with at least one electrical contact for supplying current to the display; and a frame having a section which, in use, is resiliently biased against the display to allow absorption of shock and for securing the display to the portable apparatus.
The invention will now be described, by way of example only, with reference to the accompanying drawings, in which: